1. Field of the Invention
The present invention relates to an RFID (Radio Frequency Identification) tag that performs information exchange with external equipment in a noncontact manner. Incidentally, among those skilled in the art related to the technical field of the present application, the “RFID tag” used in the specification of the present application may sometimes be called an “inlay for RFID tag” by regarding the “RFID tag” as an internal component member (inlay) for “RFID tag.” Or alternatively, in some cases, this “RFID tag” may be referred to as “a radio IC tag.” Also, a noncontact type IC card is included in this “RFID tag.”
2. Description of the Related Art
In recent years, there have been proposed various RFID tags that perform information exchange with external equipment represented by a reader/writer in a noncontact manner by use of radio waves. As one kind of this RFID tag, there has been proposed an RFID tag in which an antenna pattern for radio communication and an IC chip are mounted on a base sheet made of plastics or paper. A conceived mode of using an RFID tag of this type is such that the RFID tag is stuck to an article and the like and performs the identification of the article by exchanging information on the article with external equipment.
In this mode of using an RFID tag of this type, there is excepted a fraudulent use in which an RFID tag stuck to an article is stripped off from the article and then this RFID tag is stuck to another article in order to mislead external equipment in the identification of the article, whereby, for example, an expensive article is obtained as if it were an inexpensive one. Therefore, a technique for preventing such fraudulent uses is demanded.
Against this background, there have been proposed techniques for making communication impossible by causing an antenna pattern to be broken down during the stripping of an RFID tag (refer to the U.S. Patent Laid-Open No. 2003/075608, the U.S. Pat. No. 6,421,013 and the National Publication of International Patent Application No. 2003-524811, for example).
FIGS. 1(A) and 1(B) are a front view and a side view, respectively, of an RFID tag of conventional technique in a condition before stripping.
An RFID tag 1 shown in FIGS. 1(A) and 1(B) is constituted by an antenna pattern 12 provided on a base sheet 13, an IC chip 11 connected to the antenna pattern 12 via a bump 16, and a cover sheet 14 bonded to the base sheet with an adhesive 15 so as to cover the antenna pattern 12 and the IC chip 11.
This RFID tag 1 is used, with the base sheet 13 side thereof stuck to an article, and the adhesive force of the adhesive 15 is weaker than the adhesive force with which the base sheet 13 side of the RFID tag 1 is bonded to the article. For this reason, when the RFID tag 1 is stripped off by a person who attempts fraudulent uses, the cover sheet 14 comes off from the base sheet 13.
Also, the antenna pattern 12 has portions that are weak in adhesion to the base sheet 13 from place to place.
FIGS. 2(A) and 2(B) are a front view and a side view, respectively, of an RFID tag of conventional technique in a condition after stripping.
When the cover sheet 14 shown in FIGS. 1(A) and 1(B) is stripped off from the base sheet 13, the antenna pattern 12 comes off together with the cover sheet 14 in a portion 12a with weak adhesion to the base sheet 13, whereby the antenna pattern 12 loses the function as a communication antenna and communication becomes impossible.
As a technique for preventing fraudulent uses, there is also proposed a technique in which a dedicated pattern that is broken down during stripping is provided in the RFID tag in addition to the antenna pattern and a breakdown of the dedicated pattern is detected by use of an IC chip.
FIGS. 3(A) and 3(B) are a view of another RFID tag of conventional technique in a condition, respectively, before and after stripping.
An RFID tag 2 shown in FIGS. 3(A) and 3(B) is provided with an antenna pattern 22, an IC chip 21 connected to the antenna pattern 22, and a breakdown pattern 23 that is cause to conduct by a conductive ink 24, and as with the RFID tag 1 shown in FIGS. 1(A) and 1(B), the RFID tag 2 is also provided with a base sheet and a cover sheet, which are omitted in the figures.
Also in the case of this RFID tag 2, if the RFID tag 2 is stripped off by a person who attempts fraudulent uses, the cover sheet comes off from the base sheet. And in this RFID tag 2, the conductive ink 24 spatters while the cover sheet is coming off, thereby bringing the breakdown pattern 23 into an insulating condition, and the IC chip 21 detects this insulating condition in the breakdown pattern 23. Also, the breakdown is visually ascertained from the conductive ink 24 that has spattered.
In the case of the RFID tag 2 shown in FIGS. 3(A) and 3(B), the antenna pattern 22 and its communication function are maintained even when the cover sheet comes off, and the antenna pattern 22 informs external equipment of the stripping of the RFID tag 2 during communication with the external equipment.
However, in conventional techniques as described above, the fact that due to the stripping of an RFID tag, part of the tag is broken down and the place where the tag is broken down are clear to the person who attempts fraudulent uses. Therefore, this gives the person who attempts fraudulent uses a motivation and an opportunity for repairing the broken place, posing the problem that the prevention of fraudulent uses is insufficient.